Conventionally, gas turbines have transition pieces installed thereto for leading combustion gas of high temperature and high pressure generated in a combustor to a turbine portion efficiently. The inlet portion of such a transition piece has a configuration so as to be connected to a combustor basket where combustion gas is generated, while the outlet portion thereof is configured so as to be connected to a flow path of the turbine. The shell portion of a transition piece has a welded construction in which plates having cooling holes are combined. Furthermore, the outlet portion has a rib mounted thereon for reinforcement.
Additionally, a transition piece seal is arranged to each of the inside diameter side and the outside diameter side at the outlet of the transition piece, thereby restraining leakage of the cooling air from a portion connected to the turbine portion. In this way, by introducing the cooling air to the outlet portion of the transition piece and by preventing the cooling air from leaking with the transition piece seal, the outlet of a transition piece is cooled by using the outlet air of a compressor. The construction of a conventional combustor of a gas turbine will be explained again hereinafter by referring to the drawings.
FIG. 8 is a schematic drawing showing a conventional combustor of a gas turbine. FIG. 9 is a view of a transition piece of the combustor seen from the outlet side. In FIG. 8, a combustor 100 of a gas turbine consists of a combustor basket 110 of a cylindrical shape and a transition piece 120 which is to be engaged into an opening 111 of the combustor basket 110. The transition piece 120 is comprised of a member of a cylindrical shape and has the opening 111 of the combustor basket 110 inserted and engaged into an inlet portion 121 thereof.
The transition piece 120 has a cross-sectional area thereof gradually narrowed from the inlet portion 121 thereof, and as shown in FIG. 9, the outlet portion 122 thereof is shaped in a rectangle that is curved to be shaped into a sector. An illustration is omitted to indicate the above-mentioned welded construction of a shell portion of the transition piece 120 in which plates having cooling holes are combined. The transition piece 120 has the outlet portion 122 thereof equipped with a seal-support portion 123 of a circular shape and which has a concave cross section on its periphery. The seal-support portion 123 is engaged with the outlet portion 122 of the transition piece 120 and fixed by welding.
Now, back to FIG. 8, the combustor 100 of the gas turbine has the outlet portion 122 of the transition piece 120 connected to a combustion passageway 210 of a turbine 200. The inlet of the combustion passageway 210 is formed by an inner shroud 230 and an outer shroud 240 which support Turbine Row 1 stationary blades 220 on both ends. The transition piece 120 has the outlet portion 122 thereof located at the inlet of the combustion passageway 210 and fixed to a casing (not illustrated). A gap between the outlet portion 122 of the transition piece 120 and the combustion passageway 210 of the turbine 200 is sealed by a circular sealing member 125 that has a y-shaped cross-sectional configuration.
The sealing member 125 has a hook-shaped tip 126 thereof inserted into a concave portion of the seal-support portion 123 which is provided to the outlet 122 of the transition piece 120 and has a forked-into-two portion 127 thereof engaged with the shrouds 230 and 240 of Turbine Row 1 stationary blades 220. In a combustor 100 of this gas turbine, pre-mixed air generated in the combustor basket 110 and ignited is ejected into a combustion room 128 of the transition piece 120 and burns, becoming a high temperature combustion gas. The combustion gas proceeds through the inside of the transition piece 120 and is then blown into the combustion passageway 210 of the turbine 200 from the outlet portion 122 thereof as shown with arrow marks C.
As an embodiment of a cooling construction of the above-mentioned transition piece is disclosed a cooling panel of a gas turbine. (For example, see Japanese Patent Application Published 2002-511126.) Also, a combustor of a gas turbine is disclosed. (See Japanese Patent Application Laid Open 2003-65071, for example.)
However, the above-mentioned conventional cooling construction of a transition piece has a non-uniform cooling effect at the outlet portion of a transition piece, and there is a potentiality of deformation caused by having this portion exposed to combustion gas and heated.